1. Field of the Invention
The present invention relates to a servo motor with a built-in drive circuit. In particular, the present invention relates to a novel improvement of a servo motor for achieving a reduction in size. The reduction in size of the servo motor can be attained such that a sensor circuit board is equipped with a sensor circuit portion and a drive control circuit portion, and that a motor drive board with a power device for driving a stator winding and the sensor circuit board are arranged side by side in a sensor cover.
2. Description of the Related Art
A motor encoder construction may be mentioned as an example of a conventionally used servo motor with a built-in drive circuit of this type (see, for example, JP 62-278408 A and U.S. Pat. No. 5,912,541).
In the motor encoders as disclosed in JP 62-278408 A and U.S. Pat. No. 5,912,541, the motor portion is integrated with the encoder, and the drive circuit portion as a driver is constructed in the form of a casing separated from the motor main body.
The conventional motor with a brake is constructed as described above, and therefore has the following problems.
In the driver of the conventional construction, isolation between the boards is necessary since the sensor board for the encoder, the drive control board for drive control, and the motor drive board for driving the stator winding exist independently each other. Further, it is necessary to effect mutual transmission and reception of signals, which requires a large number of ICs.
Thus, the servo motor as a whole including the driver is rather large, which leads to a serious obstacle to a reduction in the size of a machine tool, robot, or the like when a large number of servo motors are used simultaneously for multi-axis control.